1. Field of the Invention
The present invention relates to a rotary valve which is disposed between fluid flow paths, and can execute a flow rate adjustment and a flow rate shutoff of a fluid flowing within the fluid flow paths, and more particularly related to a rotary valve which can be used as a lead air control valve of a stratified scavenging two-cycle engine.
2. Description of the Related Art
Conventionally, as a valve body which is disposed between fluid flow paths, and can execute a flow rate adjustment and a flow rate shutoff of a fluid flowing within the fluid flow paths, there has been known a butterfly type throttle valve and a rotary valve. In particular, a lead air control apparatus (for example, refer to Japanese Patent Application Laid-Open (JP-A) No. 2000-328945) employing a butterfly type throttle valve as a lead air control valve of a stratified scavenging two-cycle engine or a carburetor for a two-cycle engine (for example, refer to JP-A No. 9-268918) employing a rotary type throttle valve are proposed by the applicant of the present invention, respectively.
The lead air control apparatus described in JP-A No. 2000-328945 is provided with a configuration shown in FIG. 7. In other words, a carburetor 60 having a throttle valve 61 is attached, via an insulator 67, to a first intake passage 62 connected to an intake port 57 open to a cylinder 50, and an intake side of the carburetor 60 is connected to an air cleaner 63. Within the insulator 67, there are provided a second intake passage 64 connected to the first intake passage 62, and a lead air passage 65 which is parallel to the second intake passage 64. One end of the lead air passage 65 is connected to the air cleaner 63, and the other end is connected to a scavenging port 58 open to the cylinder 50 via a connection pipe 68. A butterfly type air control valve 66 for controlling an air flow rate is provided within the lead air passage 65, and works with a throttle valve 61 provided in the second intake passage 64.
As shown in FIG. 7, an air-fuel mixture is compressed in a cylinder chamber A at a top dead center position of a piston 51. In this state, when the air-fuel mixture is ignited by a spark plug 52, the air-fuel mixture is exploded, and pushes down the piston 51. At this time point, the scavenging port 58 and a scavenging passage 59 are filled with a lead air purified by the air cleaner 63, and a crank chamber 53 is filled with the air-fuel mixture, in which a fuel and air purified by the air cleaner 63 are mixed, by the carburetor 60.
When the piston 51 moves downward, the intake port 57 is first closed, and the air-fuel mixture filled in the crank chamber 53 is compressed. Next, an exhaust port 54 is opened in accordance with the downward movement of the piston 51, and a combustion gas is discharged to an external portion through an exhaust passage 55 via a muffler 56. Subsequently, the scavenging port 58 is opened, and the lead air filled in the scavenging port 58 and the scavenging passage 59 flows into the cylinder chamber A on the basis of a pressure of the compressed air-fuel mixture within the crank chamber 53, and the remaining combustion gas is discharged from the exhaust port 54.
Thereafter, the air-fuel mixture within the crank chamber 53 flows into the cylinder chamber A. However, since the piston 51 moves upward and the exhaust port 54 is closed at this time, the air-fuel mixture is prevented from being discharged to the external portion, an amount of hydro carbon HC contained in the exhaust gas is reduced, and it is possible to reduce a loss of the fuel.
The amount of the air-fuel mixture passing through the carburetor 60 can be controlled by the throttle valve 61, and the amount of the lead air passing through the air passage 65 can be controlled by the air control valve 66. Since the throttle valve 61 and the air control valve 66 work with each other, it is possible to always keep a balance of the amount of the air-fuel mixture and the amount of the lead air, and it is possible to execute a combustion control under an optimum state.
Accordingly, in the invention described in JP-A No. 2000-328945, since the air control valve 66 is provided within the air passage 65 for the lead air within the insulator 67, there can be obtained such effects that the air control valve 66 can be provided within a limited space without requiring an area product, it is possible to make an entire length L of a whole of the engine shown in FIG. 1 short, and it is possible to obtain a light and compact stratified scavenging two-cycle engine.
Further, since the air control valve corresponding to a constituting part which has been conventionally provided between the air cleaner and the carburetor is not required, it is possible to reduce the number of the parts, and since the carburetor can employ a general carburetor, there can be obtained an effect that a cost thereof can be reduced.
Next, the carburetor for the two-cycle engine described in JP-A No. 9-268918 is provided with a configuration shown in FIG. 8. In other words, an air passage 83 is connected to a portion in a scavenging passage 82 connecting a scavenging port 81 and a crank chamber 87 of a two-cycle engine, the portion close to the scavenging port 81. A check valve 84 allowing an air flow toward the scavenging passage 82 is provided in the air passage 83.
An air control valve 71 is provided for controlling an amount of air supplied to the air passage 83 from an air cleaner 72, and a rotary type throttle valve 73 is provided as the air control valve 71. Further, the configuration is made such that an air-fuel mixture is supplied to the crank chamber 87 from the air cleaner 72 via a carburetor 70 and a check valve 86. In order to open and close the throttle valve 73 of the air control valve 71 so as to work with an opening and closing motion of the throttle valve 74 in the carburetor 70, an operating lever 88 for driving the throttle valve 74 and a lever (not shown) for actuating the throttle valve 73 are connected to each other by a connection rod 75 so as to freely adjust a mutual interval between the both.
The carburetor for the two-cycle engine described in JP-A No. 9-268918 takes on the same actuation as that of the lead air control apparatus described in JP-A No. 2000-328945. When the air-fuel mixture compressed in an upper portion of a piston 77 is ignited by a spark plug 78, the piston 77 descends by an explosion energy of the air-fuel mixture. The combustion gas is discharged to the external portion from a discharge port 79 via an exhaust muffler on the basis of the descending motion of the piston 77, the scavenging port 81 is subsequently opened, and the lead air filled in the scavenging port 81 and the scavenging passage 82 flows into a cylinder chamber B on the basis of the pressure of the compressed air-fuel mixture within the crank chamber 87 and the remaining combustion gas is discharged from the exhaust port 79.
Next, the air-fuel mixture in the crank chamber 87 flows into the cylinder chamber B via the scavenging passage 82 and the scavenging port 81. The lead air inflows first in a state in which the air flowing into the cylinder chamber B from the scavenging port 81 and the air-fuel mixture flowing into the cylinder chamber B from the crank chamber 87 via the scavenging passage 82 and the scavenging port 81 are not mixed but separated, and the air-fuel mixture next flows in.
Next, when the piston 77 moves into an ascending stroke from the bottom dead center and reaches a position near the top dead center, the crank chamber 87 becomes in a negative pressure state, the check valve 86 of an intake port 85 is opened, and the air-fuel mixture generated in the carburetor 70 is sucked into the crank chamber 87 from the intake port 85.
Further, the check valve 84 is opened on the basis of the negative pressure of the crank chamber 87, and the air is sucked into the crank chamber 87 from the air cleaner 72 via the air control valve 71, the air passage 83, the check valve 84 and the scavenging passage 82. When the piston 77 reaches approximately the top dead center in the manner mentioned above, there is achieved a state in which the crank chamber 87 is filled with the air-fuel mixture, and the scavenging passage 82 and the scavenging port 81 are filled only with the air.
In the invention described in JP-A No. 9-268918, it is possible to lock an end portion of the connection rod 75 for driving the throttle valve 74 of the carburetor 70 and the throttle valve 73 of the air control valve 71 in an interlocking manner, by selecting an adjusting hole of an operating lever 88 or an adjusting hole of the lever (not shown) of the air control valve 71. Accordingly, it is possible to obtain an optimum opening degree of the throttle valve 73 in the air control valve 71 with respect to an opening degree of the throttle valve 74.
Accordingly, since it is possible to flow out only the air first flowing into the cylinder chamber B at the scavenging stroke to the exhaust port 79 together with the combustion gas, and hold the air-fuel mixture flowing into the cylinder chamber B after the lead air in the cylinder chamber B, a scavenging efficiency can be made high. As a result, it is possible to reduce an amount of an unburned component (HC) contained in the exhaust gas, thereby effectively using the fuel with no loss. Therefore, there can be achieved an effect that an output of the two-cycle engine cab be increased.
In the invention described in JP-A No. 2000-328945, since the lead air control apparatus employs the butterfly type throttle valve and the throttle valve shaft, it is necessary to use and assemble screws or the like for connecting the throttle valve and the throttle valve shaft. Accordingly, if a length of the air passage in the intake side or the cylinder side from an installing position of the valve is long, it is hard to insert a tool and an assembling work or the like is hard to be executed. Therefore, the valve arranged position is limited to a position in which the assembling work can be executed by the tool. Further, it is necessary to bear the throttle valve shaft at both ends thereof, an accuracy of working positions of both holes for bearing the throttle valve shaft is required.
Although, in the invention described in JP-A No. 9-268918, the rotary type throttle valve 5 is employed in the air control valve C, in order to keep a sealing performance in the rotary type throttle valve 5, it is required to configure an interval between an outer peripheral surface of the valve and an inner diameter surface of the body minimum. In order to form a minimum fixed interval, it is necessary to form the outer peripheral surface of the valve and the inner diameter surface of the body in accordance with an accurate working.